1. Field of the Invention
This invention relates to a serial impact printer, and more particularly to a serial impact printer having two printing modes.
2. Description of the Prior Art
Impact printers are useful in multiple copy capability and flexibility of print receiving paper compared with non-impact printers such as ink-jet printers and thermal printers. Impact printers are classified by printing mode into two types, one being a formed-character printing type for printing fully formed characters on the print receiving paper on a platen, and the other being a dot-matrix type for impacting the print receiving paper on the platen by selected ones of a plurality of wires. These types of impact printers have different features in use. The formed-character printing type is excellent in print quality compared with the dot matrix type, while the latter is advantageous in printing speed. Therefore, these types of impact printers are separately used in accordance with printing purposes. This requires at least two impact printers in order to respond to all kinds of printing requirements.
For this purpose, there has been proposed, as disclosed in the Japanese Patent Disclosure No. 54-156725, a multi-head serial printer in which two types of printing heads, i.e., a formed-character printing head and a dot matrix printing head, are mounted on a single carriage, and one of the two printing heads is selectively used for printing in accordance with the printing purpose. In the multi-head serial printer, because the two printing-heads are mounted at different positions on the carriage, printing strokes for such printing heads are apart from each other by a distance equal to an interval between the two printing heads. This means that the two printing heads have different left or right margins. Further, two printing heads on the single carriage make the carriage massive, whereby a complicated position-control circuit is required for positioning the massive carriage at a commanded position.